In Doppler frequency measurement equipment used in navigational systems, it is essential to obtain accurate measurements including an exact indication of any partial Doppler cycles present in the measurement. Some prior art devices use analog multiplying techniques on the input signal or a combination of several input signals to increase the resolution of the Doppler measurement prior to digitizing the measurement. Another technique for making accurate measurements of partial Doppler cycles is embodied in copending patent application Ser. No. 025,260 by Stulting et al. and assigned to the common assignee, entitled, "Method and Apparatus For Measuring Received Doppler Cycles For a Specified Period of Time". The technique used there counts both full and partial cycles of Doppler input signal utilizing a counter having clock pulses many times the expected Doppler frequency. The partial cycle count is compared to the full cycle count for the same period and a calculation made to determine the fractional count.
The prior art systems introduce a high degree of complexity in their circuits and/or require counters capable of responding to very high frequency clock pulses.